1. Field of the Invention
The present invention relates to motor vehicles and in particular to a motor vehicle with a knock control system.
2. Description of Related Art
Suzuki et al. (U.S. Pat. No. 4,426,975) is directed to an ignition timing control system for internal combustion engines. Suzuki teaches a device configured to correct the basic ignition timing in response to knocking in an internal combustion engine. The ignition timing is further modified according to the engine speed. This is done to prevent excessive retarding of the ignition timing and decreasing the torque under low speed operation as well as to prevent exhaust gas temperatures from rising above allowable limits of the system at high speed operations. In other words, Suzuki teaches a system for limiting the amount of ignition timing retard that occurs in response to knocking in order to maintain preferred operating conditions in the engine.
Takasuka (U.S. Pat. No. 5,335,744) is directed to a knock control system for an automobile internal combustion engine. Takasuka teaches a knock control system in combination with an engine that is equipped with traction control. When traction control (to prevent slipping of the wheels) is in process, the fuel mixture supplied to the engine may be lean. If knock control is operating simultaneously, ignition timing retard (caused by knock control) may lead to high temperatures that can degrade catalysts and affect emissions. To prevent this from happening, the Takasuka design includes a method of turning off the knock control to prevent the ignition timing retard so as to further prevent the degradation of components in the air/fuel mixture.
In the Takasuka design, temperatures high enough to degrade components of the air/fuel mixture will generally occur at higher speed ranges. Therefore, in the Takasuka design, knock control may only be turned off if traction control is in process when the engine speed is high. In other words, knock control may be turned off when traction control is in progress and the engine speed is high.
Yoneyama (U.S. Pat. No. 4,838,228) is directed to an engine timing control apparatus that includes a control circuit for calculating an appropriate value for engine ignition timing. The Yoneyama design includes a method for calculating ignition timing in response to knock control sensors. Corrections to the ignition timing to account for knock control are made according to the engine speed and the engine load.
The Yoneyama method uses correction factors that are dependent on the operating condition of the engine and are associated with three knock control regions. The first region is an unnecessary knock control region that occurs for low engine speeds and low engine loads. The second region is a necessary knock control region that occurs for intermediate engine speeds and loads. The third region is an impossible knock control region that occurs for high engine speeds and loads. In the unnecessary knock control region knock control is not used because knock will generally not occur in this region. In the necessary knock control region ignition timing can be adjusted to reduce knock using information from knock sensors. In the impossible knock control region, increased noise and vibrations may make knock detection difficult, so adjustments to ignition timing for knock control may be based on estimated rather than measured values.
Britsch et al. (U.S. Pat. No. 4,542,727) is directed to an internal combustion engine operating control system and method. Britsch teaches a system where a standard or permissible knocking signal is generated by the control system and this signal is compared with a measured knocking signal. When the measured signal is above the permissible signal, some engine parameter such as air/fuel ratio, ignition timing or other parameter may be adjusted to reduce the knock. In some cases, the permissible knock signal may be modified according to an engine operating parameter, such as temperature or speed. Britsch teaches that the parameter could be engine speed, so that at low engine speed the permissible knocking signal could be modified to allow for greater knocking in the engine, since knocking is relatively harmless at low-speed conditions of the engine.
There is a need in the art for a system and method that addresses the shortcomings of the prior art discussed above.